High microwave power (1000 W) electron cyclotron resonance CH4/H-2/Ar discharges produce etch rates for In0.5Ga0.5P, Al0.5In0.5P0.5, and Al0.5Ga0.5P of similar to 2000 Angstrom min(-1) at moderate RF power levels (150 W) and low pressure (1.5 mTorr). This is approximately a factor of five faster than for conventional reactive ion etching conditions where much higher ion energies are necessary. The etched surfaces are smooth over a wide range of CH4-to-H-2 ratios and microwave powers. AlInP is more resistant to preferential loss of P from the near-surface during etching than is InGaP. While the etching is ion-driven, pure Ar discharges produce rough surfaces and the CH4/H-2 is necessary in the achievement of acceptable morphologies.